A flexible display is expected to be used in a wide range from a mobile foldable display to a large screen display. A flexible display is strongly desired to be realized as a next-generation display that is lightweight and is easily accommodated. Especially, a liquid crystal display element is applicable to both of a transmission-type display system and a reflection-type display system, and thus has a possibility of being applied to a flexible display that provides superb visible recognizability in any of various illumination environments.
A liquid crystal display device may be curved or folded when being used for a certain use. When the liquid crystal display device is curved or folded, the thickness of a liquid crystal layer is changed due to a difference in the degree of deflection between a transistor array substrate and a counter substrate facing each other. In addition, the positional relationship between pixel electrodes in the array substrate and color filters in the counter substrate is changed (pixel defect occurs) due to a shift of the substrates in a planar direction of the substrates. There is a problem that the display quality of the liquid crystal display device is decreased due to these phenomena. In order to solve the problem, a technology of using a polymer to form a connection portion that bonds and secures the two substrates to each other. A technique used most commonly for forming the connection portion of the polymer is an ultraviolet patterning polymerization method.
Japanese Laid-Open Patent Publication No. 2006-162825 describes a basic mechanism of this technique. A mixed solution of a liquid crystal material and a monomer is exposed to ultraviolet light to form a pattern. As a result, the molecular weight and the form of the monomer are rapidly changed because of a photopolymerization reaction. The photopolymerization reaction changes the monomer into a polymer, and thus phase separation of the liquid crystal material and the monomer advances. Specifically, a polymerization reaction of the monomer, which is ultraviolet-polymerizable, is started when the monomer is irradiated with ultraviolet light. By the influence of the resultant concentration variance in the monomer, the monomer is condensed in a part exposed to the ultraviolet light and the liquid crystal material is condensed in a part not exposed to the ultraviolet light. This causes the phase separation. The condensed monomer is polymerized by being irradiated with the ultraviolet light, resulting in the formation of a polymer in the part exposed to the ultraviolet light.
According to the technique described in Japanese Laid-Open Patent Publication No. 2006-162825, the monomer in the part exposed to the ultraviolet light is changed to a polymer by the photopolymerization reaction. However, since the manner of the monomer moving to the part exposed to the ultraviolet light is by diffusion, the time required to form the polymer is significantly long.